From: Mark Brown <broonie@kernel.org>
To: Zev Weiss <zev@bewilderbeest.net>
Cc: Rob Herring <robh@kernel.org>,
devicetree@vger.kernel.org, openbmc@lists.ozlabs.org,
linux-kernel@vger.kernel.org, Liam Girdwood <lgirdwood@gmail.com>,
Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>,
Laxman Dewangan <ldewangan@nvidia.com>,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
Naresh Solanki <naresh.solanki@9elements.com>,
Patrick Rudolph <patrick.rudolph@9elements.com>
Subject: Re: [PATCH 2/3] dt-bindings: regulator: Add regulator-output bindingg
Date: Fri, 28 Oct 2022 16:51:54 +0100 [thread overview]
Message-ID: <Y1v6migO2PNV4ksW@sirena.org.uk> (raw)
In-Reply-To: <Y1tWpikPogEtV0+x@hatter.bewilderbeest.net>
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On Thu, Oct 27, 2022 at 09:12:22PM -0700, Zev Weiss wrote:
> I can see why it might look that way, but I'd argue it's actually not. The
> systems this is intended to support provide power to entirely separate
> external devices -- think of a power distribution unit that might have
> arbitrary things plugged into it. It seems to me like a property of the
> hardware that those things shouldn't have their power supply turned off (or
> on) just because a controller in the PDU rebooted.
We don't turn things off on reboot? We don't do anything in particular
on reboot...
> > I guess it easy
> > to understand in case of Linux which disables unclaimed regulators
> > during. But what if other system/firmware does not behave like that?
> In this case, then no change would be needed -- a system that (unlike Linux)
> doesn't twiddle regulator state on its own would just continue to not do
> that.
We don't turn unclaimed regulators off until userspace has had a chance
to start, if there's some problem with system integrators arranging to
do this we can look into how that works, for example making the delay
tunable. I don't think this is really meaningfully different from a
driver deciding to turn things off from a binding point of view.
> > And what is the "external actor"? OS is not an external actor?
> It's admittedly a bit vague, but I couldn't think of a clearer way to
> express what is a sort of nebulous concept -- essentially, some entity
> outside the "driver" (or analogous software component) using the information
> in the device-tree. In many common cases this would essentially mean "a
> human user", since in the PDU-like systems I'm targeting here the only thing
> that should ever be deciding to turn the regulator on or off is an operator
> logged in to the system to manually enable or disable an outlet. I was
> aiming to leave the wording a bit more general though, since in some other
> context I could imagine some other piece of software toggling things
> automatedly (e.g. lights getting turned on and off on a schedule or
> something, if that's what happens to be plugged in).
This is policy stuff, it doesn't translate into DTs at all.
> > I could not get the problem you want to solve with this property - I
> > looked at cover letter and at commit msg.
> The problem is that a driver deciding on its own to enable or disable the
> regulator (e.g. during boot or shutdown) would be a critical failure for the
> kind of systems I'm aiming to support.
If the driver is doing something like this it should be addressed in the
driver.
> > I can only imagine that you want to keep regulator on, after last its
> > user disappears... but for what purpose? Do you expect that after system
> > shutdown the pin will stay high so regulator will be also on? If so, you
> > need hardware design, e.g. with some pull up (if control is over GPIO).
> As described above, the regulators involved here (in these sorts of PDU-like
> systems) provide power for external systems and devices. It is critical
> that the controller's boot and shutdown sequences not alter the state of the
> regulator.
This really sounds like a full stack system integration problem, not
something that can be resolved with one software component.
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next prev parent reply other threads:[~2022-10-28 15:53 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-25 22:03 [PATCH 0/3] regulator: Add DT support for regulator-output connectors Zev Weiss
2022-09-25 22:03 ` [PATCH 1/3] regulator: devres: Add devm_regulator_bulk_get_exclusive() Zev Weiss
2022-09-25 22:03 ` [PATCH 2/3] dt-bindings: regulator: Add regulator-output binding Zev Weiss
2022-09-29 21:07 ` Rob Herring
2022-09-29 21:27 ` Zev Weiss
2022-10-27 18:42 ` Zev Weiss
[not found] ` <ee37b5a1-5afc-71b3-f777-add295d9ce17@linaro.org>
2022-10-28 4:12 ` [PATCH 2/3] dt-bindings: regulator: Add regulator-output bindingg Zev Weiss
2022-10-28 15:51 ` Mark Brown [this message]
2022-10-28 19:44 ` Zev Weiss
2022-10-31 15:45 ` Mark Brown
2022-10-31 18:50 ` Zev Weiss
2022-10-27 18:54 ` [PATCH 2/3] dt-bindings: regulator: Add regulator-output binding Mark Brown
2022-09-25 22:03 ` [PATCH 3/3] regulator: userspace-consumer: Handle regulator-output DT nodes Zev Weiss
2022-09-29 6:29 ` [PATCH 0/3] regulator: Add DT support for regulator-output connectors Patrick Rudolph
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